(1) Field of the Invention
The invention relates to an apparatus and method for confirming the integrity of a seal system positioned within a subterranean well Christmas tree and one or more conduits, such as production tubing and/or casing, held therein.
(2) Background of the Invention
Casing and production tubing are disposed within a subterranean well subsequent to the drilling, workover or completion thereof. A length of casing having the largest diameter is first introduced at the top of the well through which a smaller diameter length of casing also is introduced for extension below the lowermost end of the largest diameter casing and secured to the lowermost end of the largest diameter casing by means of a liner hanger. Thereafter, the series of casing conduit sections may be telescopically concentrically disposed within the well, depending upon the depth of the well and the location of the production zone or zones. Typically, the smallest diameter casing section will carry interior thereof a length of production tubing. The uppermost conduits are secured together at the top surface of the well through a "Christmas tree" which is a valving system holding the casing and production conduits in sealed relationship and having valving mechanisms for controlling fluid flow therethrough.
Conventional methods of testing wellhead and Christmas tree cavities defined between the housing of the Christmas tree and the outer diameter of one of the conduit members employ the use of oils or water fluids. Temperatures encountered during flowing conditions of high pressure, high temperature wells have the potential to heat these fluids to a point where the fluid expansion can potentially collapse the metal seal sleeves and elastomeric seals. Additionally, the use of water can ultimately cause corrosion to metal parts, and the use of oil can ultimately degrade elastomers.
The present invention is directed to the problems as above addressed.